Irradiated resins



United States Patent IRRADIATED RESINS Donald A. Guthrie, Cranford, N.J., and David W. Young,

Homewood, 111., assignors to Esso Research and Engineering Company, acorporation of Delaware No Drawing. Application September 27, 1955Serial No. 537,064

11 Claims. (Cl. 204-158) This invention relates to the irradiation ofresins and more particularly relates to gamma irradiation of sulfonatedpolystyrene ion exchange resins. Still more particularly, the presentinvention relates to a method for preparing improved sulfonatedpolystyrene ion exchange resins by gamma irradiation, to the improvedresins so produced and to uses of these improved resins.

The present application is a -continuation-in-part of Serial No.468,991, filed November 15, 1954, by David W. Young, one of the presentapplicants.

Ion exchange resins are well known in the art. A particularly useful andwidely used type of ion exchange resin is a sulfonated polystyreneresin. Such resins have been employed heretofore to advantage in a widevariety of applications such as water softeners, catalysts inhydrocarbon conversion processes and the like. Although these particularion exchange resins have provided outstanding performance, they have thedisadvantage of being relatively unstable to hydrolysis, particularly atelevated temperatures and pressures.

It has now been found that ion exchange resins and more particularlysulfonated polystyrene resins can be substantially improved by exposingor subjecting the resins to high intensity radiation. The irradiatedresins are characterized by their substantially increased stability tohydrolysis, which is particularly noticeable at elevated temperatures.In addition it has been found that the improved resins of the presentinvention are outstanding catalysts for a process wherein olefinichydrocarbons are hydrated to form oxygenated products comprisingalcohols and ethers.

THE SULFONATED POLYSTYRENE RESINS The present invention is particularlyapplicable to sulfonated polystyrene resins and especially to sulfonatedpolystyrene resins which contain as constituent monomers about 50 to 99weight percent of styrene and about 1 to 50 weight percent of divinylbenzene, preferably 75 to 98% by weight of styrene and 2 to 25 weightpercent of divinyl benzene, and especially about 84 to 98 weight percentof styrene and 2 to 16 weight percent of divinyl benzene. Such resinsare well known in the art and are marketed commercially and aretherefore particularly useful in the present invention. It will beunderstood, however, that the present invention is also applicable toother ion exchange resins. For example, instead of styrene, it ispermissible to use other monovinyl aromatic compounds such as panethylstyrene, p-ethyl styrene, a-methyl styrene, a-methyl p-methyl styrene orother dimethyl styrenes, p-chlorostyrene, dichlorostyrenes, and soforth. While, in general, compounds having the vinyl group in paraposition to the alkyl or halogen substituents are preferred, otherisomers are similarly useful also. Likewise, instead of using divinylbenzene as the chemical cross-linking agent, other polyvinyl arylcompounds may be used such as divinyl toluene, divinyl xylene, divinylethyl benzene, divinyl chlorobenzene, divinyl ethers, divinylnaphthalene, and the like. It will also be understood that the presentinvention is applicable to such resins containing minor amounts ofmonomers other than styrene and divinyl benzene (or similar compounds)such as, for example, butadiene, isoprene and isobutylene.

These resins may be prepared in a variety of ways from a variety of rawmaterials. For instance the sulfonation or equivalent acid treatment maybe applied to a monomer such as styrene which is subsequentlypolymerized into a suitable high molecular weight ionexchange resin.Preferably, however, the organic resin is formed first and then the acidgroups are introduced by treating the solid resin in suitably subdividedor granulated form. j

The polymerization of the aforementioned ingredients can be carried outby any of the Well-known methods, e. g., by simple heating at anelevated temperature such as 100 C. for a suitable length of time, suchas 10 days. However, it is preferable to use a catalytic amount of anoxygen-yielding compound such as benzoyl peroxide, ammonium persulfate,potassium persulfate, sodium perchlorate, sodium perborate, ozone,ozonides, etc., with temperatures of about 20-120 C., and apolymerization time inversely of a week to as short as a few hours. Thepolymerization can be carried out either in homogeneous phase or inemulsion. For instance, satisfactory materials can be prepared accordingto the procedure described in Patent No. 2,089,444 or 2,500,149.Depending on the technique employed, the polymeric resin can be producedeither in the form of nearly spherical hard granules of a proper sizefor further use, or the polymeric resin can be produced in the form oflarger masses which are reduced to the desired particle size by crushingor cutting. I

-In making the aforementioned organic materials into the desiredcation-exchange resins, they are sulfonated or phosphonated in a mannerotherwise well known so as to introduce on the average about 0.25 to 3,preferably about 0.5 to 2, inorganic acid radicals per benzene nucleusof the polymeric resin. Suitable sulfonation agents include concentratedor fuming sulfuric acid, chlorosulfonic acid, sulfur trioxide innitrobenzene, etc. An excess of the sulfonating agent is used. Dependingon the sulfonating agent used, temperature of sulfonation may be in therange of about --20 to 200 0., preferably 20 to +50 C. in the case ofchlorosulfonic acid. Higher temperatures are best with sulfuric acid.The resin is preferably in a relatively coarse particle size such as20l00 mesh so as to be suitable for direct use in the eventual olefinhydration process. Thus, the subdivided copolymer, e. g., one containing90% of combined styrene and 10% of combined divinyl benzene, can bemixed with an excess of chlorosulfonic acid, e. g. about 6 parts acidper part of copolymer, briefly heated at reflux temperature for about 3minutes and subsequently the mixture is held at room temperature forabout 50 hours. Finally, a large excess of water is added to themixture, and the latter is then filtered, Washed and dried. In a typicaloperation a yield of about 235% of sulfonated resin (based on copolymer)is thus obtained. This sulfonated resin contains an average of about1.77 sulfonic acid groups in each of its aromatic nucei. At lowertemperatures a less extensively sulfonated product is obtained, e. g.,one containing a single sulfonate group per aromatic ring.

To minimize physical disintegration of the hard copolymer duringsulfonation, the granules may first be assesses swell ed in a suitablesolvent such as benzene, toluene,

Xylene, carbon tetrachloride; trichlcsroethylene, tetra chloroethyleneand the like, in a manner substantially as described in Patent No.2,500,149. For instance, some granulated copolymers cambe swelled bycontact with 10..to 50 volume percent of a solvent suchastetrachloroethylene to much asfabout -170%.of--the.originalcopolymerlvolu'me; However, in most'instances even slight swelling ishelpful in reducing subsequentidisintegration.

Afterdraining E excess solvent, the swollen granules are then treatedwithbne of the sulfonating agents mentioned above, .e. g, 98% sulfuricacid.

The sulfonation. reaction starts at the surface of. each granule and iscontinued until .the entire granule has been penetrated by the acid to.give a complete reaction.

Thef'streirgth of the acid decreases as the sulfonation proceeds; Aftereompletion theireaction-the remainingacidis washed outwith water,.orfirst neutralizedand then washed; As water replaces the acid, furtherswelling ofthe granulesrnay occur, up to about 25%. Too rapid dilutionwith water tends to weaken the resin structure content may lead todisintegration of the granules upon 7 subsequentcontact with water. 'Forinstance, a resin originally containing 55% moisture may be dried out at60% relative humidity to a equilibrium moisture content sulfonation. Thepreferred commercial resins usually have an acidity of aboutmilliequiva'lents per gram- THE 'IRRADIATION OF THE RESINS Radioactivematerials providing high energy ionizing radiation are useful in thepresent invention. The preferred radioactive materials are thoseemitting gamma rays. Materials emitting onlybeta rays may be employedbut are less effective than materials emitting radiation comprisinggamma rays. Also, if desired, neutrons may be employed alone or incombination particularly with gamma rays, the latter beinga preferredcombination.

One source foriradioactive materials is an atomic pile. Large quantitiesof radioactive by products or waste materials from these atomic pilesare now available. The

of on1y about-30%. When such a partially dried out resin is placedwater, water absorption may be-so rapid that severe disintegration ofthe granules takes place. 7

' -It .willbe understood, of course, that thedescribed polystyrenetypeion-exchange resins as well as their preparation are Well known andreadily available as commercial products; 7 For instance, a particularlyuseful resin for purposes of the present inventionfis a commercialcation-exchange resin knownunder the trade name Dowex 50X8 and made bythe DowChemical Company.

This is asulfonated; resinous copojly rner of about: 92%' styrene and 8%divinyl benzene, which contains about 5A to 50% moisture and about 1 2to 16% sulfurin the sulfonate form,- based on anhydrous resin. Thismaterial has approximately the same acidity as benzene sulfonic acid..-Useful materials 1 ofthis type'having a somewhat higher divinyl :benzenecontent are also marketed under the names of Dowex; 5 0Xl2 aswellasDowex 50Xl6.

All ofthese materials are brown in color- Another material isDOWBX'SOWXK'WhlChiS cream colored and especially stable in themechanical sense due. to virtually completeabsence of internalstrainsas'shown by inspection under polarized light. This material is preparedby introducing the sulfonic acid groups into the polymer under specialconditions so that oxidation of the polymer is almost completelyavoided.

Other sulfonated polystyrene ion-exchange resins are sold by the Rohmand Haas Company under the amberlite trademark, particularlyamberliteJR-lZO. All of these 'sulfonic acid type ion-exchange resinsare usually sold in the formof sodium salts which can bereadilyconverted or regenerated to the acid type by washing with an aqueoussolution of sulfuricor hydrochloric acid in a manner well lcnoivn byitself; In such regeneration the hydrogen ions ofthe wash acid replacethe sodium ions of the resin. The ion-exchange resins in their free acidform have an acidity of about 2 to milliequivalents per grain, dependingon the resin base and extent of present invention provides a practicalutilization ofsuch by-product or waste materials which at presentrepresent a disposal problem. due to their steady accumulation. Thesefission by-products of atomic piles include radioactive elements withatomic numbers ranging from '30 (zinc) to 63 (europium). These wastematerials. are formed in the course of converting uranium,'plutonium orother fissionable material in atomic reactors.

A'lsoynaturally occurring radioactive materials such as radium orthorium maybe employed asthe radioactive material in. the presentinvention. In addition, variousmaterials made. radioactive byexpostrreto neutron radiation, such as'radioactive cobalt (Co europiurn europium','etc., may also be used for the purposes or the present invention.Also, the *fission gamma radiation and the. neutron flux existing in. anatomic re actor may beemployed. This latter method is an'es'peciallydesirable method when anatomic reactor is readily available.

*In addition to utilizing high intensity radiation emitted fromradioactive material, othersources of radiation may be employed; forexample, the high energybeamsemitted by ion accelerators, such as theVan der Graaf generator. Using such generators accelerated beams ofelectrons,

,protons,"'deuterons and the like are producedand these too will servethe purposes of the present invention. 'ln accordance with'the presentinvention, the sulfo} nated polystyrene resins are subjected to, highintensity ionizing radiation. -Generally, radiation dosages amountizugtoj about0.l"to 500 megaroentg'ens may be employed. Preferably radiationdosages of about 1m 50 megaroentgens, andmore' preferably about 2 tomegaroentgens. are employed. Itfhas been found that a radiation dosageof about 5 megaroentgens is. particularly useful Radiation sources of astrength equivalent to'a'bout 5O cuties to 1,000 kilocuries of cobalt?may be employed to carry out the irradiation of the resins. Radiationintensi-' ties in the range of about 10 r0 10, preferably about 10 to 10roentgens per hour are desirable. Preferably irradiation'times of about0.5 to hours wili'be employed. However, shorter or longer irradiationtimes may be employed if desired. The time willdepend :of course uponthe strength of 'theisource and the radiation dosage rate. 'Theirradiation may be carried out from about 0 F. up to a'temperatureslightly below the softening point of the resin. Room temperature isusually preferred however. Higher or lower temperaturesfmay' be employedif desired. However, if tom and generally is 'notpreferred. However, ifan atomic reactor is readily available; it"rnay be desired to passtheresinin' a slurry forrn in such an inert liquid diluent throughconduits disposed -in the atomic reactor.

USES OF THE IRRADIATED RESINS The use of ion exchange resins ascatalysts for hydrocarbon conversion processes has been proposed.Sulfonated polystyrene resins have been found to be particularlyeffective catalysts for the direct hydration of olefins to producealcohols and ethers. It has been found that the present irradiatedsulfonated polystyrene resins are particularly useful in such a process.More specifically, it has be n found that in such a process theirradiated resins are less susceptible to sulfur loss and are,therefore, more efiective catalysts.

More specifically, the present invention is particularly applicable tothe hydration of normal olefins in the C to C range. Accordingly, theinvention is particularly applicable to the hydration of hydrocarbonfractions which contain substantial amounts of ethylene, propylene, orn-butylenes, or mixtures thereof. A particularly useful hydrocarbonfraction is one containing about 25 to 100% by Weight of propylene. Thehydrocarbon feed rate or space velocity may be in the range of about 0.5to 4 volumes of liquid olefin per volume of catalyst per hour. Theproduct of the hydration consists largely of a mixture of thecorresponding alcohols and ethers. Thus, isopropyl alcohol anddiisopropyl ether are derived by hydration of propylene. The ratio ofalcohol to ether in the hydrated product may range from about 95:5 to20:80, depending on the specific reaction conditions employed. Inparticular, relatively low olefin feed rates, e. g., those not in excessof about 1.5 volumes per volume of catalyst per hour, favor theformation of ether relative to alcohol, especially at temperatures ofabout 350 F. or more.

The reaction temperature is usually kept at about 250 to 425 F.,preferably at about 315 to 375 F., the optimum depending somewhat on theparticular olefin treated and the product desired. For instance,temperatures of at least 330 F. are preferred where high ether yieldsare wanted, whereas lower temperatures are preferred when alcohol isdesired most.

When substantial amounts of isobutylene are present in the feed inadmixture with normal olefins, it may be desirable to treat the mixturefirst at low temperature, e. g., below 250 F., so as to hydrate theisoolefin with a minimum of polymer formation. tions the normal olefinspass through the reaction zone substantially unconverted, but can thenbe hydrated in accordance with the present invention in a separate stepsubsequent to the hydration of the isoolefin. At temperatures aboveabout 450 F., the resins tend to be relatively unstable and have a shortcatalyst life. Enough pressure is preferably employed to keep the waterof hydration at least partly in liquid phase. Accordingly, reactionpressures may range from 600 to 3,000 p. s. i. g., preferably 1,000 to1,500 p. s. i. g.

The catalyst is normally disposed in the reaction zone in the form of apacked bed of granular particles ranging in size from about 20 to 60 or100 mesh. The reaction mixture is passed through such a bed eitherupwardly or downwardly, the latter being preferred in most instances.

Water of hydration is fed to the reaction zone in a ratio of about 0.3to 3 moles per mole of olefin, depending at least in part on the productdistribution desired. For instance, water/olefin mole ratios of at least2 will favor the formation of alcohol. Conversely, at low feed rates,and temperatures above 330 F. and with water/olefin mole ratios of oneor less, a hydrated product containing a very large proportion of ethercan be produced. 0

The hydration product is a valuable additive for gasoline or diesel fuelwhich, in addition, may contain other conventional materials such asanti-oxidants, solvent oil, rust inhibitors, and so on. The ethers andalcohols are also useful as solvents, chemicals, etc.

Under such condiing the scope of the present invention in any way.

Example I The following commercially available sulfonated polystyreneresins were studied for their stability to hydrolysis at elevatedtemperatures:

TABLE I.ION EXCHANGE RESINS STUDIED Approximate composition, weight,

percent 2 Monomers 3 Resin acid 1 Sulfonate groups Styrene Divinylbenzene Dower; 50-X2 98 2 gowex 55%: 96 4 owex 5 92 Dowex 50 X8 92 3About 40 weight Dowex 50Xl2. 88 12 Percent base? Dowex 50X16 84 1s totaldry Dowex 50X24 76 24 Amberlite IR- 92 8 1 Trade names.

2 Dry basis.

3 Based on copolymer prior to sulionation. 4 Sodium salt.

The above commercially available sulfonated polystrene resins areprepared generally by preparing a copolymer of styrene and divinylbenzene, sulfonating the copolymer and then convertin the sulfonatedcopolymer into a sodium salt. It will be noted that two of the resinsstudied were in the form of the sodium salt, whereas the other resinswere converted to contain free acid groups by simply washing the resinseveral times with dilute hydrochloric acid solution.

Several of the above mentioned resins were subjected to irradiation inthe following manner:

Approximately 50 gm. of each of the wet resins were placed in individual2-ounce bottles which were tightly stoppered. These bottles containingthe resin samples were then placed in the center of a cylindrical cobaltgamma ray source at room temperature for varying periods of time. Theradiation intensity to which they were exposed was about 220,000roentgens/hour.

The non-irradiated resins and irradiated resins were then subjected to ahydrolysis test which was carried out in the following manner:

Twenty grams of the resin (calculated on the dry basis) were introducedtogether with 600 cc. of distilled water into a one-liter bomb. The bombwas then sealed and shaken for 7 days at 356 F. After this time the bombwas cooled, opened, and the resin was removed and analyzed for sulfur tocompare with the sulfur content of the resin before hydrolysis.

The results of this hydrolysis test have been found to correlate quiteclosely with the results obtained when employing such resins ascatalysts in the hydration of C to C normal olefins to prepare ethersand alcohols. More specifically, the loss of sulfonic acid groups in thehydrolysis test (as indicated by the loss of sulfur) is a measure of theloss of activity of the catalyst in' the olefin hydration process.

' feed/volume of catalyst/hour during this'runl' The followingresults'were found in the hydrolysis test: I

TABLE 'rr-sTABr rTY or SULFONATED POLYSTYRENE RESINS 'ro HYDRQLYSIS 1 ag a i Megaroentgens.

2 Sodium salt.

It will be noted that the non-irradiated resin acids lost from about tosulfur in the hydrolysis test or became totally water soluble. Watersolubility of the resin is, of source, undesirable. The sulfur loss wasessentially independent of the amount of divinyl benzene in thesulfonated polystyrene resin, although with more than 4% of divinylbenzene, the resin was at least insoluble in water. On the other hand,it will be noted that a substantial increase in stability to hydrolysiswas realized when employing an irradiated resin in accordance with thisinvention. More specifically, it will be noted that the I The aboveresults indicate that the sodium salts of the V resin acids are morestable than the resin acids themselves, but are still not as stable asthe irradiated resin acids.= In addition, it will be noted that theirradiation of a resin acid sodium salt (Amberlite Ill-120) using 5megaroentgens increased still further the stability of the resin bydecreasing the sulfur loss through hydrolysis from 10% to about 5%. i

7 Example II 60% water) was placed in a 900 cc. tube which was tightlystoppered. This tube was then placed in the center of a cobalt source atroom temperature for a suflicient period of time to receive 5megaroentgens of garnma radiation (16.7 hours at about 300,000 R./hr.).

The propylene 'feed stream employed in the hydration process containedabout 95%propylene and about 5%.

saturated hydrocarbons (principally propane).

- The hydration process was carried outas follows:

A stainless steel reaction tube was filled with .500 .bulk

cc. of the wet resin. At a pressure 0f'l000 pbs. i. and a 7 temperaturein the reactionzone of 300 F., the propylene feedwas injected above thecatalyst along with water in s a downflow'operation', using'a ratio ofonemole of propylene/rnoleofwa'terf The'flow rate'was one volume of'After equilibrium conditions had been established the conversion andselectivity of the process were determined; The

8 7 total reaction time in this experiment was about 2.5 hours. Forcomparison purposes a similar resin was employed as a 'catalyst in thehydration process except that a second resin was not subjected toirradiation.

The following results were found: 7 P

TABLE III.HYDRATION OF PROPYLEbiE USING DOWEX 50X8 I PercentSelectivities Z Resin irradiation dose conversion 1 Ether Alcohol 1Defined as the percent conversion of propylene in the feed to oxygenatedproducts. I r

Defined as the percent of the product appearing as either ether alcohol.

The results set forth above in Table III show that'the irradiation ofthe ion exchange resin improved its activity as a catalyst for thehydration of propylene. More specifically, it will be noted that the useof the irradiated resin polystyrene-divinyl benzene'resin to highrenergyionizing radiation of an intensity and duration sutficient to in-- surestability to hydrolysis. e

2. A method for improving the stability of1 a-s ul-' fonated polystyreneresin to hydrolysis which comprises subjecting a sulfonated polystyreneresin to high "energy ionizing radiation amounting to about 0.1 to 500megaroentgens,.the constituent monomers of said resin being about 50 to99% by weight of styrene and aboutl to 50% by weight of divinyl benzene,said sulfonated resin.con-- taining about 0.25 to 3 sulfonate groups perbenzene nucleus.

3. A method for improving the stability of a sulfonated polystyreneresin to hydrolysis whichcomprises subjecting a sulfonated polystyreneresin'to gamma radiation amounting to about 1' to 50 megaroentgens, theconstituent monomers of said resin being about'7 5% 'to 98% by weight ofstyrene and about 2.to 25 by weight. of divinyl benzene, said'sulfonated resin containing about 0.5 to 2 sulfonate groups per'benzenenucleus. 1

4. Method according'to claim 3 wherein the irradiation is carried out atabout room temperature. W

5. Method according to claim 3 wherein the radiation dosage is about 5megaro'entgens. a

6; A sulfonated polystyrene-divinyl benzene resin which has beensubjected to frorn Ol to 500 megaroentgens of high energy ionizingradiation comprising gamma rays.

7. A sulfonated polystyrene resin having improved stability tohydrolysis prepared by the method defined by claim 2.. i

8. A sulfonated polystyrene resin having improved stability tohydrolysis prepared by the method defined by claim 3.

9. In a process for converting olefinic' hydrocarbons into an oxygenatedproduct by passing a feed mixture of'olefinic hydrocarbon feed and waterat least partly in liquid phase through a closed conversion zoneunder'hydration conditions at a temperature between about 250 to 425 F.and at a pressure between 1000 and 1500 p. s. i. g. over. a catalyst,wherein the mole ratio of water/olefinjs be? tween about 0.3 and 3, theimprovement which comprises converting said olefinic hydrocarbon feed toan oxygenated product in the presence of an irradiated sulfonatedpolystyrene resin prepared by the ,method of claiml .as a I catalyst. a

.10; In a process for converting a normalolefinic hy-,

drocarbon feed having 2 to .4 carbon atoms per molecule into .anoxygenated product by passing a' 'feedmixture;

7 10 of said normal olefinic hydrocarbonrfeed and Water at 11. Processaccording to claim 10 wherein the hydroleast partly in liquid phasethrough a closed conversion carbon feed contains about 25 to 100% byWeight of zone under hydration conditions at a temperature betweenpropylene. about 250 to 425 F. and at a pressure between about u t 1,000and 1,500 p. s. i. g over a catalyst wherein the mole 5 emmmes Cited mthe me of tms Paent ratio of Water/olefin is between about 0.3 and 3,the im- UNITED STATES PATENTS provement which comprises converting saidnormal ole- 2,477,380 Kreps et aL July 26, 1949 finic hydrocarbon feedto an oxygenated product in the w presence of an irradiated sulfonatedpolystyrene resin OTHER REFZRENCES prepared by the method of claim 2 asa catalyst. 10 Nature, pp. 76-77, July 11, 1953.

1. A METHOD WHICH COMPRISES SUBJECTING A SULFONATED POLYSTYRENE-DIVINYLBENZENE RESIN TO HIGH ENERGY IONIZING RADIATION OF AN INTENSITY ANDDURATION SUFFICIENT TO INSURE STABILITY TO HYDROLYSIS.